The invention relates to a video synchronizer having a velocity compensator therein for correcting velocity errors on incoming video signals derived from video tape recorders (VTR).
Velocity compensation is well known in digital time base correctors. An improved method of time base correction is disclosed in British patent application (U.S. Pat. No. 3,995,112) which describes the concept of `look-ahead` velocity compensation for time base correctors that effectively monitors the velocity error from the tape recorder that is occurring while the line of information is being written in to one of the time base corrector (TBC) line stores. The output from the velocity compensation circuit then modifies the output velocity correspondingly.
Such a TBC look-ahead velocity compensator requires a small number of individual analogue stores corresponding to the number of lines being stored in the TBC. Now if this method was extended to cover a framestore for example with perhaps 485 or even 585 lines the number of individual stores would become immense and would result in extreme difficulty in physically realising the system.